Silicon containing lubricating compositions



3,085,104 SHLILON CONTAENENG LUBRHCATING (JOB iifif'aiTKONS Paul V. Smith, in, Snnningdale, England, David W.

Yonng, Homewood, ill., and Delmar L. Cottle, Highland Paris, NJ, assignors to Essa Research and Engineering (Iompany, a corporation of Delaware No Brawing. Originai application Apr. 30, 1953, Ser. No. 352,284. Divided and this appiication July 30, 1956, Ser. No. 600,668

9 Claims. ((11. Nth-443$) This invention relates to synthetic lubricating compositions. Particularly it relates to synthetic lubricants having utility at both high and loW temperatures. More particularly it relates to new and improved synthetic lubricants of the silicon containing type which exhibit outstanding characteristics as to pour point and low temperature viscosity. Still more particularly, the invention relates to synthetic lubricating compositions which comprise branch chain silicate esters.

The present application is a division of Serial No. 352,- 284, filed April 30, 1953, for Paul V. Smith, Jr., David W. Young, Delmer L. Cottle and Arnold J. Morway, now abandoned.

In the lubricating art, considerable progress has been realized in recent years in the production of lubricants characterized by one or more specific properties and adapted for specific uses. In general this progress is attributed to two developments, new and improved refining techniques, and addition agents capable of imparting particular properties to available lubricants. Thus, viscosity index improvers and pour point depressors are added to available automotive lubricants to render the lubricants more adaptable to change in temperature conditions. There are, of course, limits upon the range of effectiveness of these addition agents and certain requirements cannot be met in every instance by means of additives.

With the development of the turbo-jet and the turboprop type aircraft engine, which operate at peak efiiciency at extremely high altitudes, there has developed a corresponding need for a lubricant which is efficacious at the extremely low temperatures encountered at high altitudes or in frigid areas. Engine manufacturers and operations personnel dealing with these turbine engines must be supplied with a lubricant possessing exceptional low viscosities at low temperatures and, at the same time, having satisfactory lubricating qualities at high temperatures.

Mineral lubricating oils which exhibit satisfactory low temperature viscosities have generally been found to have flash points that are dangerously low and high tempera-; In other ture viscosities that are below those required. words, when the mineral oil is thin enough at low temperatures, it is too volatile and too thin to provide satisfactory lubricity at higher temperatures. It has been found that, generally speaking, additive agents do not satisfactorily furnish the required characteristics.

Recently, in an elfort to obtain the superior lubricants needed for these uses, a new field has been explored, namely, the synthesis of lubricants from various materials. Esters represent one class of materials which have attracted unusual interest as synthetic lubricants. Esters are generally characterized by high viscosity indices and flash points and lower pour points than mineral oils of a 3,085,104 Patented Apr. 9, 1963 corresponding viscosity. It has also recently been found that the inclusion of a silicon atom in an ester results in improved properties. It has now been found and forms the object of this invention, that the tetra alkyl silicates of the branch chain alcohols known to the art as Oxo alcohols are materials which have outstanding properties as synthetic lubricants in that their low and high temperature characteristics are well within the requirements necessary for lubrication of the engines described above.

The new and improved synthetic lubricants of this invention have the following general formula:

(RO) Si In the formula above, R represents an alkyl group which is derived from an Oxo alcohol having from 6 to about 20 carbon atoms. The Oxo alcohols are highly branched chain aliphatic alcohols prepared by the 0x0 synthesis. This process may be described as being the catalytic reaction of an olefin with carbon monoxide and hydrogen. The reaction occurs at temperatures in order of 300- 40-0 F., at pressures in the range of about 1000 to 3000 psi, in the presence of a suitable catalyst, ordinarily a heavy metal carbonyl such as cobalt carbonyl. The resulting aldehyde is subsequently hydrogenated to a primary alcohol. This process is described in United States Patent No. 2,327,066, issued to Roelen in 1943.

It has been found that particularly desirable alcohols for the formation of the silicates of this invention can be prepared by the application of the Oxo synthesis to polymers and copolymers of C and C monoolefins. These monoolefins are readily available in petroleum refinery streams, and processes for their conversion to liquid copolymers have been worked out by the art. One such process, known as U.O.P. polymerization, consists of passing the olefin-containing stream in liquid phase in contact with an acid catalyst comprising phosphoric acid impregnated on kieselguhr. Other acidic catalysts, such as phosphoric acid or copper phosphate impregnated on silica gel, sulfuric acid, Friedel-Crafts catalysts, activated clays, silica-alumina, copper pyrophosphate, etc. may be used. Suitable conditions when employing phosphoric acid catalysts of the U.O.P. type are temperatures of 300 F. to 500 F., pressures from 250 to 5,000 p.s.i. and feed stocks comprising refinery streams containing propylene and mixed butylenes. Suitable feed stocks, for example, may contain from 15 to 60 mol percent propylene, from 0.5 to 15 mol percent butylenes, and from 0.1 to 10 mol percent isobutylene, the remaining being saturated hydrocarbons. Other suitable feed stocks are the dimer and trimer of isobutylene.

The preferred Oxo alcohol employed in forming the silicates of this invention are those having from 6 to 20 carbon atoms derived from olefin copolymers having from 5 to 19 carbon atoms. In preparing these Oxo alcohols the desired olefin fraction is segregated from the crude olefin polymer product by fractionation.

The following table, for example, shows the structure and percent composition of C Oxo alcohols prepared from a C olefin stream which had been fractionated from the products obtained by the phosphoric acid polymeriza tion of refinery gas streams containing propylene and mixed nand isobutylenes.

Structure of Ca Oxo alcohols prepared from Percent C -C4 copolymer heptenes C 2 I C -OCGC-OH 29 t t CO-O-C-OCOH 25 C O CO-( J-GOOH 17 O C-C-( J-OC-CCOH 16 0 C-CO-C( C-C-OH (I) O O-O( J-GGOOH 2. 3

O C-:I- J)CGC-OOH 1. 4

a-alkyl alkanols 4. 3 Others 5.0

It will be noted that 0x0 alcohols derived from the olefins produced by C -C polymerization are mostly methyl substituted.

In general the silicates of the instant invention may be simply prepared by methods known to the art. One molecular proportion of SiCL; is reacted with four molecular proportions of the desired alcohol by slowly adding the SiCl to the alcohol. Temperature of the reaction should be held between about 20 C. and 70 C. The temperature is then increased to about 133 C. and nitrogen passes through the system to remove HCl. The unreacted alcohol is removed by heating in a vacuum or by other stripping means'with which the art is familiar.

The invention will be more clearly explained by reference to the following examples, which are illustrative rather than limiting.

EXAMPLE 1 170 g. of SiCl was reacted with 572 g. of C OX0 alcohol. The reaction was conducted in a one liter round bottomed flask fitted with a Water cooled condenser. The SiCl was very slowly added to the alcohol from a dropping funnel. The temperature \was held at 37 C. to 46 C. as the SiCL; was added. After completion of the addition of SiCl the temperature was increased to 133 C. and nitrogen was passed through the system. To remove unreacted alcohol the material was heated under vacuum to 200 C. pot temperature at 2 mm. mercury pressure. The final weight of the colorless oil was 357 g.

EXAMPLES 2 AND 3 Using the procedure outlined above, the C and C Oxo alcohol esters of silicic acid were prepared.

The synthetic lubricants prepared in Examples 1 to 3 above were submitted to the standard ASTM viscosity determinations, the flash point determination, and the ASTM pour point determination. Results of the determinations are set out in Table lbelow.

An examination of the data in the table above shows the excellent viscosity properties of the synchetic lubricants in accordance with the instant invention.

In another concept of this invention, silicates of mercaptans are contemplated. In this embodiment a mercaptan, such as a C to C alkyl mercaptan is reacted with SiCl to form a material having the general formula The materials are prepared as described in connection with the alcohol esters above. The following table illustrates this embodiment of the inventive concept.

Table II Moles of S1014 1 1 1 Moles of mercaptan. 4.1 4.1 4.1 Name of mercaptan t-Octyl t-Hexadecyl t-Dodecyl mercaptan mercaptan mercaptan Time of reaction, hours 8 8 8 Mole percent yield (200 C. pot temp. stripped product at 2 mm. H 74 63 79 Inspections:

Vls. at 210 F. (cs.). 4. 62 5. 53 6.27 Viscosity index. 183 179 174 Actual pour, F -65 -60 55 Flash point, F 405 420 430 Vis. at -40 F. (cs.)- 1, 125 1, 420 1, 59a Hydrolytic stability test 1 Passed Passed Passed 1 5 cc. of the oil is placed in 50 cc. of water and boiled for 1 hour. At the end of this period the water is tested for acidity and its neutralization number taken. Failure is indicated by precipitation of Si(OH)4 and increase in acid number.

According to another concept of the instant invention, synthetic lubricants of the complex type are prepared by reacting together SiCl a glycol or a thioglycol, and an alcohol or a mercaptan. The complex type of molecule may be said to have the formula:

In this formula, R is as defined above, that is, an alkyl group containing from 6 to 20 carbon atoms. X is selected from the group consisting of oxygen and sulfur. R represents the aliphatic portion of the glycol chosen and is an alkylene group containing from about 1 to about 30 carbon atoms.

Among the glycols operable may be mentioned ethylene glycol, propylene glycol, butylene glycol, the various polyalkylene glycols, such as polymethylene, polyethylene, polypropylene and polybutylene glycols, thioglycols, such as thiodiglycol, and the like. The diols, such as 1,3 butane diol, etc. may also be used.

These complex types of synthetic lubricants are prepared by reacting SiCl with a glycol, removing all the HCl formed by blowing with nitrogen, and adding additional alcohol to react with the remaining chlorine atoms. If it is desired to build molecules containing sulfur atoms, a

5 sodium hydroxide solution, water and then dried and distilled under vacuum. The following table will give more specific data on the method of preparation and on the inspection data of the product.

Table III Charge 169.8 g. SiC14, 2 moles sicn, 2moles SiO1 45.0 g. tetra- 1 mole butane- 1 mole tetramethylene diol 1-3, 6 methylene glycol, 390.0 g. moles 03 x0 glycol, 6 moles Os Oxo alcohol alcohol 013 0x0 alcohol Final weight of product, stripped, grams- 278. 5 550 Not det. Inspections:

Cs. vis. at 100 F- 25.1 22. 3 40. 6 CS. vis. at 210 F. 0. 7 6.4 8.9 Cs. vls. at 40 F. 1,866 1, 433 5,780 Cs. vis. at 65 F- 8,180 5, 270 Solid Pour point, F 75 75 60 Flash point, F 405 415 445 Hydrolytic stability test I Passed Passed Passed 1 Same as in Table II.

The synthetic lubricating composition described in detail above may also be used to prep-are grease compositions which have properties of high and low temperature resistance that are very desirable in the lubrication of moving metal parts where an oil composition cannot be used. The grease compositions are prepared by procedures familiar to the art. Two such grease compositions are described in detail below:

EXAMPLE 4 Percent Complex lithium soap 1 15.0 C Oxo silicate 84.0 Phenyl alpha naphthylamine. 1.0

1 Lithium soaps of crotonic and hydrogenated fish oil acids in 1 :1 mole ratios.

The lithium soaps and the C 0x0 silicates were slurried together and then heated While agitating to 500 F. At this temperature the phenyl alpha naphthylamine was added to the molten grease and the homogeneous fluid mass poured into pans in shallow layers for quick cooling. The grease when cold was transferred to a grease kettle and worked smooth, filtered and packaged.

EXAMPLE 5 Percent Lithium complex soap 12.0 C Oxo silicate 87.0 Phenyl mpha naphthylamine 1.0

Lithium soap of acetic and hydrogenated fish oil acids in 1 :1 mole ratios.

Prepared similar to Example 4.

1 Brown, short fiber smooth. 2 Excellent, no separation or leakage thru shield.

Although the above examples show the use of lithium soaps, any of the commonly used soap forming metals may be used. For instance, sodium, calcium, barium,

strontium, lead and the like are operable in this concept of the invention.

It will be seen that the novel synthetic lubricating compositions of the instant invention are versatile materials which have many applications which make them of value to industry as a whole. In addition to the uses described above the materials of invention may be used as plasticizers for plastics and synthetic rubber compositions. They may be used as blending agents for mineral lubrieating oils to increase the high temperature performance of such oils. Various compatible additive agents may be added to the synthetic lubricants of invention to increase special characteristics. For instance, their viscosities may be improved by incorporation of polysilicones of various molecular weight ranges. Other additive agents such as viscosity index improvers, pour point depressants, detergent inhibitors, oxidation inhibitors, extreme pressure improving agents, and the like may be added to the oils per se or to blends containing them.

To summarize briefly, the instant invention relates to silicon containing synthetic lubricants having excellent high and low temperature characteristics. The lubricants of the instant invention may be pictorially described by the following formula:

wherein R is an alkyl group containing from 6 to 20 carbon atoms, wherein X is selected from the group of oxygen and sulfur, and wherein Y is either (RX)- or the radical X-R-XSi(XR) 'R' being an alkylene radical derived from a glycol or a thioglycol.

These new synthetic lubricants may be thickened to a grease consistency with a minor, but grease forming amount, preferably from 2% to 20% by weight, of a metallic soap of a high molecular weight fatty acid, preferably the lithium soap of a mixture of crotonic and hydrogenated fish oil acids.

What is claimed is:

1. A compound having the formula RO) SiOR'OSi (OR) 3 wherein R is a branched chain alkyl radical of at least 6 carbon atoms and R is an alkylene radical having at least 2 carbon atoms.

2. A synthetic lubricating composition having outstanding high and low temperature properties which comprises a compound of the formula wherein R is an alkyl group containing from 6 to 20 carbon atoms, wherein X is selected from the group of oxygen and sulfur, and wherein R' is a glycol residue.

3. A synthetic lubricating composition according to claim 2 wherein X is oxygen, and wherein R is the combining radical of a C 0x0 alcohol.

4. A composition according to claim 2 wherein X is oxygen and wherein R is the combining radical of a C OX0 alcohol.

5. A composition according to claim 2 wherein X is oxygen and wherein R is the combining radical of a C Oxo alcohol.

6. A composition according to claim 2 wherein X is oxygen, wherein R is the combining radical of a C OX0 alcohol and wherein R is the combining radical of tetramethylene glycol.

7. A compound having the formula (RO) SiOR'OSi(OR) 3 wherein R is a branched chain alkyl radical of at least 6 carbon atoms and R is an alkylene radical having at 7 least 3 carbon atoms in a chain between the adjacent oxygen atoms.

8. Silicon esters of the type having the general formula in which the R s and R s represent branched-chain primary alkyl s of from 6 to 18 carbon atoms.

9. A compound having the formula (R0) SiO-R'O-Si (OR) 3 wherein R is a branched chain alkyl radical of at least 6 5 carbon atoms and R is an alkylene radical having at least 2 carbon atoms in a chain between the adjacent oxygen atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,776,307 Abbott et a1 Jan. 1, 1957 

2. A SYNTHETIC LUBRICATING COMPOSITION HAVING OUTSTANDING HIGH AND LOW TEMPERATURE PROPERTIES WHICH COMPRISES A COMPOUND OF THE FORMULA 